How do I Hook leds to subwoofer (voltage)

[proskater123]

So I bought a bunch of led strips

http://cgi.ebay.com/Car-Red-15-SMD-LED-Bul...=item56388cea6f

And was planning on hooking them to my amp in my car. So everytime my sub hit, the lights lit up. My problem is that the amp is putting out 500 watts to each sub. 1000 watts total. I'm not sure what to do in order to regulate the wattage going to the lights so they don't burn out and burst. Is there something that I can buy or should I be fine just hooking them straight to the amp. I know how to do the wiring just not how to keep to much power from going into the lights. Any ideas?

[MRGRIM]

I could be wrong here as I never paid much attention when it came to electronics, I have no doubt someone else will correct me.

You’ll want to run this parallel to the cable that’s already going to the sub, you’ll need to put a resistor between the battery and the LED strip. I think you can work our what Omz the resistor needs to be.

[Sparda]

A simple relay might do it, you would have to use a resistor (or a few) to lower the current from the amp.

For example:

http://www.maplin.co.uk/Module.aspx?ModuleNo=6436 except it's only rated to carry 480W at 12V (40A). I don't know enough to do the numbers but the type of resistor you are probably looking for is a few of these in parallel, they will have to have the same resistance as the sub.

Alternatively get some thing like this: http://www.electronickits.com/kit/complete/elec/k126.htm and be done with it.

[moonlit]

I could be wrong here as I never paid much attention when it came to electronics, I have no doubt someone else will correct me.

You’ll want to run this parallel to the cable that’s already going to the sub, you’ll need to put a resistor between the battery and the LED strip. I think you can work our what Omz the resistor needs to be.

That, basically (minus the bit about the battery, just hook to the speaker terminals, + to +, - to -), though given that the output voltages will probably peak somewhere around 12v or so anyway, you might not need to add the resistor (those strips are rated for 12v anyway). If they seem too bright, throw in a resistor.

[Sparda]

That, basically (minus the bit about the battery, just hook to the speaker terminals, + to +, - to -), though given that the output voltages will probably peak somewhere around 12v or so anyway, you might not need to add the resistor (those strips are rated for 12v anyway). If they seem too bright, throw in a resistor.

There is a good chance the LEDs have a far lower resistance than the subs, so all the current will try to go threw the LEDs.

[moonlit]

There is a good chance the LEDs have a far lower resistance than the subs, so all the current will try to go threw the LEDs.

Nah, it'll be fine, try it and see. Consider the fact that those lights are designed to be hooked to a 12v car battery which can pump 100s of Amps at any given time, I don't think a little amp is gonna give 'em much trouble.

[proskater123]

Yeah I don't know how to figure out how many resisters I will need. That's my stand still ATM. And sparda the device you listed won't strobe with the bass. It will turn on for 1 - 5 seconds then turn off. I will need it to be even shorter than that.

[moonlit]

The lights are rated for 12v, the amplifier will likely peak around 12v (possibly 11-14v, depending on whether the engine's running and how good the battery is), you shouldn't need a resistor.

[metatron]

If you are that worried about burning them out just use a voltage regulator that is fixed to the value you are looking for, there about 5p each. You feed in your power source to the left leg (voltage regulator facing you, the side with the text), ground to the center and it gives you your desired voltage out the right leg, with the center remaining ground.

LM2940CT is what you are looking for.

[moonlit]

Trouble is with a vreg, he's looking for the lights to flash to the bass, and while they would do that on one, they'd trigger quite easily and not vary in brightness at all. I suppose the proper way to do it would be to use a digital potentiometer and a PWM circuit, but I imagine that's a little more complex than he was hoping.

I still reckon hooking them up directly will be fine, though. The way to be certain is to not turn up the volume very high to begin with, then ramp up until the LEDs look to be their brightest without burning.

[beakmyn]

What you want is something that's called a color organ or light organ. Typically you have a small board mounted microphone or have a sound input that picks up the sound level and translates it to light output. Way back in 1996 I built one from scratch and had it running in my dorm room. It ran several lights through a series of relays. For you its much simpler.

Personally I would not mount a LED in line with the output of the amplifier, that's just asking for trouble. With the kits and a relay you can all matter of lights (think marker lights, headlights, taillights, strobes, etc).

Here's some links to various kits.

http://www.apogeekits.com/light_organ_mk114.htm

http://www.goldmine-elec-products.com/prod...&variation=

http://www.electronickits.com/kit/complete/ligh/canck185.htm

http://www.horrorseek.com/home/halloween/w...ColorOrgan.html

[h3%5kr3w]

Back when car audio modding first started really getting big, people were doing this with leds (I myself had some setup in my house). Don't run them inline. Trust me. For some reason when (or if, but most probably when) the led burns out, a high resistence spike is made on the line and will burn out either your sub or your amp. This didn't always happen, but about 1/2 the time it did.

Go get an arduino and make it a separate system from the amp and subs themselves!

[proskater123]

I knew there were devices that did that just never knew what to look for. THanks for the information. But I'm gonna try to just hook them straight to the amp. Then just bring the bass up further and further and see what happens. Now another question is how should i hook them up to the amp. Should i hook them up so that all positive wires are together and same with neg. or should i hook them up in line so that one positive is hooked to a neg and so on till i get the the amp. Which is the safest way? Its not so much the lights that im worryied about. IF they burn out then oh well. They were only 1 doller each. Its jjust that it takes two weeks for them to get here.

[moonlit]

+ to +, - to -, in parallel, and not in line, with the speaker.

[bobdole369]

wowza, the misinformation from all around just sort of conglomerates together into a big steaming pile of poo doesn't it?

There are a number of ways to light a bulb when the music gets loud. Every method I've seen discussed here will distort the living bejesus out of the sound.

Metatron, the 2940CT is a DC device. In addition as the OP is talking about using 1000W (well I seriously doubt that, maybe peak to peak or some input power measurement, but lets say 200W RMS, as I've actually got that running in the back of my PT cruiser). Ohms law says at an impedance of 4 ohms, 200W

Roughly 7 amps RMS. roughly 29V RMS. Doing the maths you get a peak of about 10A and 41V.

Looking at the datasheet - the absolute max raiting of the 2940CT is: -30V DC input, and +45V DC. So at about 230 degrees around the first cycle you are exceeding its max rating. Smoked device. Not to mention that you are really distorting the living fuck out of the signal to the sub.

Moonlit:

What? that config actually doubles the voltage seen at the diode, assuring destruction, in the event the amp is a push/pull type. The "switchable bridge" amps that would depend on the difference between the 2 channels for a voltage drop. Not too likely.

Also with a regulator, since its a high voltage AC signal, and IC based 3 terminal regulators are only DC devices, you quickly smoke them.

Read my voltage calcs above. While the amp is run on 12V, once you get past about 200W the voltage output on the speaker terminals is quite enough to kill you (really anything greater than 30V will push enough current to stop your heart you get nailed in the right spot.) Easily 30V at 200W into 4 ohms.

The safest silly light device I would consider using is a string of 60 christmas lights (old school bulbs) in parallel with the sub. It will phase shift a bit, but it won't do really fucked up things like conducting part of the cycle, and burning the rest.

h3%5kr3w and beakmyn have the most practical ideas.

Oh and h3%5kr3w - thats called the "short" before the "open". i.e. the LED short circuits, connecting the positive and negative at high voltage. Either the amps output FET self destructs (actually shorts due to the spark across the depeletion region) from the sudden voltage change, or the massive EM field on the woofer causes a blown voice coil (EMF) or both.

Then the LED opens...

In short, the best way is to use some sort of mic and controller running the LED. You don't want bad audio or broken components do you?

Proskater - you don't have a radioshack store within skating distance of you? LED's cost like 15 cents. They even have RS stores in the mall. I hope by now you've realized how horrid an idea this is.

I hope you don't really just connect an LED (which is a diode and will dead short for a good 140 degrees of the cycle while emitting light) across the output leads in parallel with a speaker. Buhbye amplifier....

[moonlit]

Given the nature of the question (that is, to wire a cheap 12v string of LEDs to an amp), the easiest way of doing it is to do as I said. Now, I agree that it's 1) not the best way, 2) not going to give the LEDs a long life, 3) going to distort the audio and 4) not advisable to spit 30v into that string of lights, but clearly it's a cheap and nasty project, and it would "work" as long as you don't ramp the volume too high.

It's also worth noting that if the amp is running bridged, those LEDs are probably gonna go pop pretty quickly if you crank it to any sort of volume but given that he said "to each speaker" I gathered that it's not. What I meant by + to +, - to - is that the positive wire of the LEDs should be connected to the positive speaker terminal, and the negative wire to the negative terminal on one single channel (requiring two strings for two channel operation).

That particular string is supposed to run on 12v and will not cause a direct short across the amplifier terminals. The chances of that string having a lower impedance than the speaker attached to it are next to nil, if for no other reason than it's very likely to have a current limiting resistor many times the resistance of the speaker itself (ignoring the fact that the 15 LEDs themselves consume power too).

[manuel]

While I do not know the answer to your question, I'd like to say THANK YOU!!!! for being one of the few people who still understands how to actually ask a question on a forum. See kids, you too can learn from the pros. (not me, proskater)

[h3%5kr3w]

To bobdole369 - Thanks.. I always wondered why that would happen...

To the OP - The way I said to do it takes a max of MAYBE $35 extra..

(All figures taken from sparkfun.com)

Arduino Pro 328 - 5V/16MHz -$19.95

Breakout Board for Electret Microphone -$7.95 (comes preassembled with op-amp and mic)

(connect the leds individually to the arduino.. priceless)

You can code it to make them blink to the music, light up for the ammount of sound coming out, or code your own light show with them...

Grand total: for 1x arduino, and 1 mic/opamp your looking at $27.90 and if your feeling a little geekier, you can go way cheaper and just buy the components you need to build your own custom arduino for around ~$10. so that would add up to about $17.90, and then you can wire them up wherever you want, later on add a laser light show if you want! And never touch the sound.

All I am saying is though it's a quick and dirty project, it may cost you more in the long run if something fails. Sorry moonlit but I gotta go with bob on this one. All I am saying is it should be kept a separate circuit whichever way you do it.

[bobdole369]

What I meant by + to +, - to - is that the positive wire of the LEDs should be connected to the positive speaker terminal, and the negative wire to the negative terminal on one single channel (requiring two strings for two channel operation).

OK excellent. Now i get what you mean. It *would* work that way (i.e. it would light up), but talk about nasty sound!

The chances of that string having a lower impedance than the speaker attached to it are next to nil, if for no other reason than it's very likely to have a current limiting resistor many times the resistance of the speaker itself (ignoring the fact that the 15 LEDs themselves consume power too).

Ah but no mention was made that there existed a current limiting resistor! Now that I've actually looked at the thing, there very well might be one buried somewhere, it'd be an SMT 1k resistor or some such. Yup this means you wouldn't fry the amp as easily.

[proskater123]

While I do not know the answer to your question, I'd like to say THANK YOU!!!! for being one of the few people who still understands how to actually ask a question on a forum. See kids, you too can learn from the pros. (not me, proskater)

Your very welcome. I read your post about it thats why I did it :)

But I do have a radio shack that I can go to in my town. Now that I read everyones post I am kinda scared to hook the lights straight to the sub. I am going to look for something that is ment for sound to light.

[metatron]

lol, I just read the above post, thought you just wanted to keep a car battery to 12V from the max of 13.5